We take familiar inorganic oxide glasses and non-oxide glasses and the liquids from which they derive to review the current understanding of their atomic structure, ranging from the local environments of individual atoms to the long-range order which can cover many interatomic distances. The structural characteristics of important glasses and melts, like silicates, borates, alumino-silicates, halides and chalcogenides, are drawn from the results of recent spectroscopy and scattering experiments. The techniques include Nuclear Magnetic Resonance (NMR) and X-ray Absorption Fine Structure (XAFS), Neutron Scattering (NS) and Small- and Wide-angle X-ray Scattering measurements (SAXS/WAXS), and are often combined with computer simulation experiments in order to obtain detailed images of structure and diffusion in the glassy as well as in the molten state. We then review the current understanding of relaxation in glasses, liquids and polyamorphic states. This includes phenomenological models and theories of rela...

Inorganic glasses, glass-forming liquids and amorphizing solids

The most common of man-made glasses have aluminosilicate compositions, and such glasses also form from rapidly cooling magmas1. Oxygen is the most abundant element in these materials, where it occupies either ‘bridging’ (BO) or ‘non-bridging’ (NBO) sites. BOs link two AlO4 or SiO4 tetrahedra, thereby providing strong, long-lived bonds between the smallest structural units of the aluminosilicate network. NBOs provide a relatively weak connection between one tetrahedral cation (Al or Si) and one or more network modifier cations — such as Ca2+or Na+ — that are not an integral part of the tetrahedral network. The relative abundance of these weakly bonded NBOs is critical in determining the thermodynamic and dynamical properties of aluminosilicate glasses and melts1,2,3. For glasses of ‘tectosilicate’ composition, where the charge of the modifier cation equals the number of aluminium atoms (as in NaAlSi3O8 or CaAl2Si2O8), the conventional view of glass structure is that only BOs are present1,4. Here we present experimental observations that contradict this view. Our NMR measurements of CaAl2Si2O8, which determine directly the relative abundances of BO and NBO, indicate that a considerable amount of NBO can be present in a tectosilicate glass. These excess NBOs will increase the entropy and heat capacity of the corresponding liquid and decrease its viscosity, as well as modifying flow and diffusion mechanisms2,3. As the most common rhyolitic magmas and the molten precursors of glass ceramics have near-tectosilicate compositions1,4, our results require a reassessment of the high-temperature liquid properties that control many processes in the Earth and in industry.

NMR evidence for excess non-bridging oxygen in an aluminosilicate glass

Aluminum cation sites with five ([5]Al) or six ([6]Al) anion neighbors are minor species in aluminosilicate glasses that are interesting in models of structure, diffusion, and viscous flow. Using 27Al NMR, we present the first direct evidence for [5]Al in a calcium-aluminosilicate glass without excess aluminum over charge-balancing cations, and quantify small concentrations of both [5]Al and [6]Al in several fluoride-containing aluminosilicate glasses. NMR techniques that enhance resolution by decreasing the effects of second-order quadrupolar broadening, including triple-quantum magic-angle spinning (3QMAS), analysis of spinning sidebands, and data collection at very high external magnetic fields (14.1 and 18.8 T), are particularly effective in accurately observing such species.

Quantification of five- and six-coordinated aluminum ions in aluminosilicate and fluoride-containing glasses by high-field, high-resolution 27Al NMR

In several series of sodium borosilicate glasses, we have applied triple-quantum magic-angle spinning (3QMAS) 11B and 17O NMR to obtain high-resolution information about short-range structure and the connections among various network structural units and their variations with composition. Oxygen-17 3QMAS spectra reveal changes in connectivities between silicate and BO3 ([3]B) and BO4 ([4]B) units, by quantifying populations of bridging oxygens such as Si−O−Si, Si−O−[3]B, Si−O−[4]B, [3]B−O−[3]B, and [4]B−O−[3]B and of nonbridging oxygens. Boron-11 MAS and 3QMAS at a magnetic field of 14.1 T allow proportions of several borate units to be determined, including [3]B in boroxol ring and nonring sites and [4]B with two, three, and four Si neighbors. By combining the 11B and 17O NMR results, detailed information on Si/B mixing in sodium borosilicates can be derived. Our results shows that [4]B is strongly associated with silicate units, nonring [3]B undergoes random mixing and ring [3]B tends to connect to bora...

Nature of Silicon−Boron Mixing in Sodium Borosilicate Glasses: A High-Resolution 11B and 17O NMR Study

Triple, quintuple and higher order multiple quantum MAS NMR of quadrupolar nuclei

A new two-dimensional magic-angle spinning NMR experiment1,2 using multiple-quantum coherences of half-integer quadrupolar nuclei was used to study 27Al sites in crystalline samples of leucite (KAlSi2O6), anorthite (CaAl2Si2O8), and kyanite (Al2SiO5), as well as CaAl2Si2O8 glass and a magnesium aluminoborate glass In the crystals, multiple sites are partially resolved and new results for isotropic chemical shifts and quadrupolar parameters are derived, using data collected at a single magnetic field Data for both leucite and anorthite are consistent with previous results that correlate chemical shifts with mean intertetrahedral bond angle Signal can be obtained from sites with quadrupolar coupling constants as large as 9 MHz, but intensities are reduced In the aluminoborate glass, peaks for sites with different Al coordination numbers are well separated The lack of such features in CaAl2Si2O8 glass rules out the presence of significant quantities of AlO5 and AlO6 groups

https://chemistry.berea.edu/articles/jacs_1996_stanford.pdf

Triple-Quantum Two-Dimensional 27Al Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopic Study of Aluminosilicate and Aluminate Crystals and Glasses

Information regarding the correct pedigree of and relationship between animals is useful for managing dairy breeding, reducing inbreeding, estimating breeding value, and establishing correct breeding programs. Additionally, the successful implementation of progeny testing is crucial for improving the genetics of dairy cattle, which depends on the availability of correct pedigree information. Incorrect pedigree information leads to bias in bull evaluation. In this study, Neogen GeneSeek Genomic Profiler (GGP) 50K SNP chips were used to identify and verify the sire of Taiwanese Holstein dairy cattle and analyze the reasons that lead to incorrect sire records. Samples were collected from 2,059 cows of 36 dairy farms, and the pedigree information was provided by breeders. The results of sire verification can be divided into three categories: submitted unconfirmed sire, submitted confirmed sire, and incorrectly submitted verified sire. Data on the sires of 1,323 (64.25%) and 572 (27.78%) dairy cows were verified and discovered, respectively. Sires of 1,895 (92.03%) dairy cattle were identified, which showed that the paternal pedigree of dairy cattle could be discovered and verified through genetic testing. An error-like analysis revealed that the data of 37 sires were incorrectly recorded because the bull's NAAB code number was incorrectly entered into the insemination records: for 19 sires, the wrong bull was recorded because the frozen semen of a bull placed in the wrong storage tank was used, 6 had no sire records, and for 12 sires, the NAAB code of the correct bull was recorded but with a wrong stud code, marketing code, or unique number for the stud or breed. To reduce recorded sire error rates by at least 27.78%, automated identification of the mated bull must be adopted to reduce human error and improve dairy breeding management on dairy farms.

S. H. Wang

Papers

Triple-Quantum Two-Dimensional 27Al Magic-Angle Spinning Nuclear Magnetic Resonance Spectroscopic Study of Aluminosilicate and Aluminate Crystals and Glasses

Sire pedigree error estimation and sire verification of the Taiwan dairy cattle population by using SNP markers.